1. Field
This application relates to a system which provides heating, air-conditioning and electrical power generation, specifically to such a system which incorporates a mechanically-enhanced vapor ejector compressor and is powered from thermal input energy.
2. Prior Art
The ability to accurately control the air temperature of human occupied compartments is highly desirable for personal comfort in all situations and a serious matter of safety in some. Because heating and air conditioning are energy-intensive, the financial and environmental cost to provide this temperature control is almost entirely determined by the efficiency of the heating, ventilation and air-conditioning (HVAC) equipment and cost of the energy that is used to power it. For a manufacturer of HVAC systems, it would seem logical to address the largest possible market by creating an HVAC system which can be powered by the common, and lowest cost, sources of input energy.
In the prior art in can be seen that, rather than this “universal” energy approach, most HVAC systems are designed instead around the concept of highly specialized optimization. While this highly specialized approach works well when all of the initial design considerations are stable, these systems are often difficult to adapt to new conditions. When operating requirements, energy sources, energy cost and the legal environment change HVAC system that had previously been excellent solutions become costly, awkward and ineffectual.
An excellent example of this can be seen in the prior art for long-haul truck HVAC systems. For many years, these input power for these systems was an engine-driven compressor for air conditioning and waste heat from the propulsion engine for heating. These engine-driven compressor put additional load on the engine and increase the fuel consumption. When the cost of fuel was relatively low, this was not a burden and the approach worked well. However, in recent years, fuel costs have dramatically increased and new legislation prevents trucks from idling their engines to provide HVAC at rest stops. The prior art of the engine-driven cooling system and waste engine heat heating system cannot be adapted to meet these new conditions. To meet the new requirements, truck manufacturers have to install an additional HVAC system which is operational only at the rest stops when the engine is off. As with other prior art, these “no-idle” HVAC solutions are highly specialized for their application and typically either consume a large amount of liquid fuel or require large batteries to supply a limited amount of operating time. These characteristics make them unsuitable for use in the normal engine running condition of on-highway operation. As a result, truck manufacturers of today are generally required to provide two separate HVAC system on every long-haul truck—one for on-highway use and one for no-idle rest stop use. The two system approach is both expensive and highly fuel intensive.
As the cost of energy increases and the environmental impact of harnessing that energy increases in relevance, it has become increasing desirable to develop an HVAC system which consumes less energy. The energy that powers the new system should be as flexible and as universally available as possible. Finally, the ideal system should always be able to use the energy source which is the lowest in cost and environmental impact. In many applications, the energy source which best meets these requirements is waste heat captured from surrounding processes. Unfortunately, past systems designed to be so powered have suffered from serious deficiencies. One known heat-powered cooling technology is the steam jet or “ejector” compressor. Cooling systems based on ejectors were developed by Ashley, U.S. Pat. No. 2,081,905 (1937) and others and were common on steam-power trains. While the energy efficiency of these systems is poor extremely poor and, for this reason as well as others, they are not commonly used today in non-industrial settings.
Ophir et al, U.S. Pat. No. 3,922,877 (1975) attempted to adapt this technology for use in automobiles by using waste heat from the internal combustion propulsion engine to boil a refrigerate to supply the motive fluid. In such systems, the amount of energy available to power the cooling system was determined solely by the amount of heat given off from the engine as no other source of heat was supplied. This presents a serious problem since a car idling in traffic may have a very high cooling requirement but very little waste engine heat available to provide that cooling. The irreconcilable disconnect between the amount of motive energy reliably available and the amount of cooling which may be required, as well as the low coefficient of performance (COP) suffered by the Ashley invention, made such systems unreliable and limited their commercial success.
One way to partially overcome the limitations of waste heat-powered systems is to increase their efficiency. Ohashi, U.S. Pat. No. 4,765,148 (1988) sought to improve the performance of ejector cooling systems by using a working fluid composed of two or more refrigerants of different saturation temperatures. Other attempts to increase efficiency were made Garris U.S. Pat. No. 5,647,221 (1997) and others who focused on achieving this through the creation of a superior ejector design. Tawse, U.S. Pat. No. 4,309,877 (1982) took a different approach by creating a co-generating total energy system incorporating an ejector cooling system which improved output stability by using waste heat supplied from multiple sources. In all these designs, several serious problems remained including a low COP and the inability to supplement waste heat with non-waste heat energy sources. Without the ability to supplement waste heat with other sources of energy, these systems become completely non-functional when waste heat is unavailable or when it is not available in insufficient quantity to meet the full input requirement of the system.
While early work improved the performance of ejector-based cooling, the COP of these systems continued to lag far behind that of both electrically-powered Rankin Cycle and heat-power absorption systems. In 1989 M. Sokolov (“Compressor Enhanced Ejector Refrigeration Cycle For Low-Grade Heat Utilization”, IEEE 899068 CH2781) presented a system which combined an ejector compressor with an electrically-powered compressor. When provided with the right combination of waste heat and electrical power, the approach worked extremely well and improved the COP of the ejector system to the point where it exceeded that of typical absorption technology. However, as with the systems that predated it, no provision was made to supplement the waste heat from non-waste energy sources. Similarly, the functional relationship between the electric boost compressor and the waste heat-powered ejector compressor was fixed thereby limiting the possibility of widely varying that portion of the total input power which came from each source.
Continued research on this approach by Henandez (Study of a Solar Booster Assisted Ejector Refrigeration System with R134a”, Journal of Solar Engineering, February 2005, Volume 127) and Varga (“Analysis of a solar-assisted ejector cooling system for air conditioning”, International Journal of Low-Carbon Technologies 4 2-8, 2009) further demonstrated that a combination of ejector and mechanical compressors could be used to more efficiently extract cooling capacity from waste heat. My own provisional Alston U.S. patent Ser. No. 61/176,063 (2009) further improves on an ejector and electric mechanical compressor system through improved control and other techniques. Unfortunately, all of these systems required both waste heat and electrical input energy. They cannot be powered from only from waste and/or non-waste heat and cannot generate their own electric power. Therefore, they must ultimately always have an external source of electric power for the compressor, fans, controls and other necessary electricity consuming components.
Fineblum, U.S. Pat. No. 4,918,937 (1990) offered the efficiency advantages of a mechanically-boosted ejector system but reduced the electrical energy requirement by using an engine-driven mechanical compressor rather than an electrically powered one. Oshitani et al., U.S. Pat. Nos. 6,729,157 (2004), 7,178,359 (2007) and 7,254,961 (2007) offered similar systems combining both ejector and engine-driven compressors in a manner which provided particular benefit for CO2-based vehicle air conditioning systems. However, these systems, like all other ejector-mechanical systems in the prior art, still require at least one non-heat source of input energy. Additionally, all require at least some amount of electrical power, none of them can use heat to generate that power.
Therefore, it can be seen that, unlike the invention which is the subject of this application, all heretofore known mechanically-boosted ejector compressor HVAC systems suffer from one or more disadvantages which limit their application and commercial usefulness in that they;
(a) cannot use thermal energy to power the boost compressor.
(b) require an external source of electrical power for mechanical compressors, heat exchanger fans, liquid pumps, control systems, flow control valves and/or electromagnetic clutches.
(c) have no means of supplementing the waste heat energy with input from a non-waste heat source.
(d) provide no means to maximize the system efficiency by modifying the boost relationship between the ejector and mechanical compressors.
(e) cannot use waste heat energy to recharge the system electric storage battery.
(f) do not provide for multiple cooling zones through independent heat exchangers.
(g) have no provision for a separate liquid cooling loop that would allow systems using high pressure or otherwise hazardous refrigerants to be entirely located outside the cooling compartment.
(h) have no means of redirecting excess waste heat-generated electrical power to applications outside the HVAC system.
(i) do not provide for a vapor-powered engine-driven mechanical ejector boost compressor or the ability to optimize the efficiency of such a compressor by adjusting the vapor inlet and discharge valve timing.
(j) do not provide for a vapor-powered engine-driven electrical power generator or the ability to optimize the efficiency of this generator by adjusting the vapor inlet and discharge valve timing.
(k) have no means of mechanically engaging and disengaging a vapor-powered engine, an electrical motor/generator and a mechanical compressor from each other in a way that allows multiple drive combinations while eliminating the friction drag of an unneeded device.(l) do not have a control circuit which adjusts the speed of the condenser fan to eliminate excess energy consumption.(m) do not continuously optimize the system high-side pressure by adjusting the rate of flow of liquid refrigerant into the boiler.